This invention relates to a semiconductor integrated circuit and to a technique which is effective when applied to a single-chip microcomputer, for example.
In a device such as a single-chip microcomputer, address signals and data signals are transferred to an external bus in synchronism with a system clock. On the other hand, external equipment such as an external memory or a peripheral interface LSI circuit is constructed in such a manner that it reads in these transferred address or data signals at the fall of the system clock. Accordingly, address and data signals input to external equipment must be delayed with respect to the system clock, for a period of time needed for the external equipment to hold the address and data signals.
In a conventional microcomputer or the like, however, the delay with respect to the system clock of address or data signals is determined by a circuit delay of an output buffer circuit or the like. The inventors of this invention have discovered that, in this case, the delay time varies with variations in the elements of the output buffer circuit, due to variations in the process of manufacturing the elements, or temperature changes, so that the holding of the address and data signals in the external equipment can be extremely unstable.